the only car that only comes with the front springs from what i remembered was the F11 Wagons.

I think you are right. The CEC person I talked to check with ACS and they basically said some 528i xDrive has rear self leveling suspension. But from my research, it looks like it is only on F11 (and maybe F7).

Please update us as I am looking to buy a set myself and I was surprised to hear that also last week

I talked to a couple of the CEC reps. One confirmed that 528i xDrive Sedan doesn't have the self leveling rear suspension. My BMW dealership also confirmed this.
So you will need the front and rear spring kit.

i no this is offtopic but saeba1 i love your rims and i have a 535xi and havent been able to figure out how to get these rims.. if u can please let me no where u got the rims the size and the tires you are using.. and also if the ride quality is still excellent this will be greatly appreciated.. ive just gotten my car and i love yours would love to make it very similar.. thanksQ

i no this is offtopic but saeba1 i love your rims and i have a 535xi and havent been able to figure out how to get these rims.. if u can please let me no where u got the rims the size and the tires you are using.. and also if the ride quality is still excellent this will be greatly appreciated.. ive just gotten my car and i love yours would love to make it very similar.. thanksQ

Which rims? The M5 replicas or the Forgestar CF5?
As you can see in my build thread, I have recently switched over to a new set of wheels and tires.

The M5s are low pressure cast replicas in non-staggered setup (4x19x8.5 ET35) with Goodyear LS2 runflats tires.
The Forgestar CF5 are in staggered setup (20x9F + 20x10R) with Hankook Ventus V12 tires.
I got them both from Alan************. Great guy to work with.

Ride quality with the LS2 are ok, but they simply don't compare to the Hankooks. The RFTs are noisier and harsher on the ride.
The new 20s combo feel much like my original 17" wheel/tire setup in terms of ride quality (but better handling due to the ACS).